The present invention relates to a method of making spool seals for use on a spool in a solenoid valve assembly, and more particularly, to an improved molding process which allows the spool seals to be formed without die parting lines on the surfaces which are used for sealing.
Spool seals are known in the art for providing a seal on spools used in solenoid valves. The spool seal is typically comprised of rubber which has been formed into an annular ring shape by a molding process, such as injection molding. Such spool seals are typically mounted at intervals along the length of the valve spool to prevent internal and external air leakage from one valve chamber to another.
Most spool seals currently in use are formed by a molding process utilizing a two-piece mold, where the parting line of the closed mold halves is positioned at the cross section of the seal where the inner and outer diameter surfaces are formed. As a result, a rib-like projection is present at the inner and outer diameter surfaces of the molded seals. This projection is commonly referred to as a parting line. This parting line can result in a poor sealing surface when the spool seal comes into contact with the spool valve and/or valve body, since the inner and outer diameter sealing surfaces of the spool seal are not smooth.
While the parting line can be removed from the molded seal by post-molding processes such as machining, grinding, or cryogenic deflashing, such additional steps add to the expense of producing the spool seal. It would be desirable to be able to produce a spool seal using a conventional molding process without the formation of parting lines on the sealing surfaces and without requiring the use of special molding or post-molding equipment.
Accordingly, there is a need in the art for an improved method of forming spool seals which eliminates parting lines at the sealing surfaces of the seal.